U.S. patent number 5,360,656 [Application Number 08/078,216] was granted by the patent office on 1994-11-01 for press felt and method of manufacturing it.
This patent grant is currently assigned to Albany International Corp.. Invention is credited to Jan Rexfelt, Sven-Arne Svensson.
United States Patent |
5,360,656 |
Rexfelt , et al. |
November 1, 1994 |
**Please see images for:
( Certificate of Correction ) ** |
Press felt and method of manufacturing it
Abstract
A press felt is devised for use in a papermaking machine, and a
method is provided for manufacturing such a press felt. The press
felt comprises a base fabric which is made of fabric of yarn
material and is endless in the machine direction of the press felt,
and one or more layers of fiber material arranged on the base
fabric. The base fabric of the press felt comprises at least one
layer composed of a spirally-wound strip made of fabric of yarn
material and having a width which is smaller than the width of the
final base fabric. Longitudinal threads of the spirally-wound
fabric strip of yarn material make an angle with the machine
direction of the press felt. The fabric strip of yarn material may
advantageously be flat-woven.
Inventors: |
Rexfelt; Jan (Halmstad,
SE), Svensson; Sven-Arne (Halmstad, SE) |
Assignee: |
Albany International Corp.
(Albany, NY)
|
Family
ID: |
20381205 |
Appl.
No.: |
08/078,216 |
Filed: |
June 15, 1993 |
PCT
Filed: |
December 17, 1991 |
PCT No.: |
PCT/SE91/00868 |
371
Date: |
June 15, 1993 |
102(e)
Date: |
June 15, 1993 |
PCT
Pub. No.: |
WO92/11411 |
PCT
Pub. Date: |
July 09, 1992 |
Foreign Application Priority Data
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Dec 17, 1990 [SE] |
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9004009-8 |
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Current U.S.
Class: |
428/193;
162/358.1; 28/135; 28/110; 139/383A; 428/192; 442/185;
139/383AA |
Current CPC
Class: |
D06H
5/005 (20130101); D21F 7/083 (20130101); Y10T
442/3033 (20150401); Y10T 428/24785 (20150115); Y10T
428/24777 (20150115) |
Current International
Class: |
D21F
7/08 (20060101); D06H 5/00 (20060101); B32B
023/02 () |
Field of
Search: |
;139/383A ;162/358.1
;428/192,193,225,229,234 ;28/110,135 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2044385 |
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Dec 1991 |
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CA |
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0464258 |
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Jan 1992 |
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EP |
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Primary Examiner: Bell; James J.
Attorney, Agent or Firm: Kane, Dalsimer, Sullivan, Kurucz,
Levy, Eisele & Richard
Claims
We claim:
1. A press felt for a papermaking machine, comprising a woven base
fabric which is made of yarn material and is endless in a machine
direction of the press felt, and at least one layer of fiber
material arranged on the base fabric, wherein said base fabric
comprises at least one layer composed of a spirally-wound fabric
strip made of yarn material and having a width which is smaller
than a width of the base fabric, longitudinal threads of the
spirally-wound fabric strip of yarn material making an angle with
said machine direction of the press felt.
2. A press felt as claimed in claim 1, wherein the fabric strip of
yarn material is flat-woven.
3. A press felt as claimed in claim 1, wherein adjacent
longitudinal edge portions of the spirally-wound fabric strip of
yarn material are so arranged that said at least one layer of the
base fabric has a substantially constant thickness over the entire
width of the base fabric.
4. A press felt as claimed in claim 3, wherein said adjacent
longitudinal edge portions of the spirally-wound fabric strip of
yarn material are arranged edge to edge.
5. A press felt as claimed in claim 3, wherein said adjacent
longitudinal edge portions of the spirally-wound fabric strip of
yarn material is overlapping.
6. A press felt as claimed in claim 1, further comprising an edge
joint provided between adjacent longitudinal edge portions of the
spirally-wound fabric strip of yarn material.
7. A press felt as claimed in claim 6, wherein said spirally-wound
fabric strip of yarn material is provided along two longitudinal
edges thereof with seam loops of known type for providing said edge
joint in cooperation with at least one separate seam thread.
8. A press felt as claimed in claim 6, wherein said adjacent
longitudinal edge portions of the spirally-wound fabric strip of
yarn material are sewn together for providing said edge joint.
9. A press felt as claimed in claim 1, wherein said base fabric
also comprises at least one further layer of fabric of yarn
material.
10. A press felt as claimed in claim 9, wherein said at least one
further fabric layer of yarn material comprises a second layer
composed of a spirally-wound fabric strip made of yarn material and
having a width which is smaller than the width of the base fabric,
longitudinal threads of the spirally-wound fabric strip of yarn
material of said second layer making an angle both with the machine
direction of the press felt and with said longitudinal threads of
the spirally-wound fabric strip of yarn material of the
first-mentioned layer.
11. A method of manufacturing a press felt for use in a papermaking
machine, said press felt having a base fabric which is made of yarn
material and is endless in a machine direction of the press felt,
and at least one layer of fiber material arranged on the base
fabric, said method comprising the steps of:
(a) manufacturing a fabric strip of yarn material, said fabric
strip having longitudinal threads in a longitudinal direction of
said fabric strip and presenting a width which is smaller than a
width of the base fabric;
(b) spirally winding said fabric strip of yarn material, to form in
the base fabric a layer of fabric of yarn material, the
longitudinal threads of the spirally-wound fabric strip of yarn
material making an angle with said machine direction of the press
felt; and
(c) fixing said at least one layer of fiber material to the base
fabric.
12. A method as claimed in claim 11, wherein the step of spirally
winding said fabric strip of yarn material is performed by spirally
winding said fabric strip of yarn material about at least two
parallel rolls.
13. A method as claimed in claim 11, comprising, prior to the step
of fixing said at least one layer of fiber material, a further step
of spirally winding said fabric strip of yarn material to form a
second layer of fabric of yarn material on the first-mentioned
layer of fabric of yarn material.
14. A method as claimed in claim 13, wherein the fabric strip of
yarn material in said first-mentioned layer and the fabric strip of
yarn material in said second layer are wound mutually crosswise,
such that the longitudinal threads of the fabric strip of yarn
material in the second layer make an angle both with said machine
direction of the press felt and with the longitudinal threads of
the fabric strip of yarn material in the first-mentioned layer.
15. A method as claimed in claim 11, comprising, prior to the step
of fixing said at least one layer of fiber material, a further step
of spirally winding a second fabric strip of yarn material, having
longitudinal threads in a longitudinal direction of said second
fabric strip and presenting a width which is smaller than said
width of the base fabric, to form a second layer of fabric of yarn
material on the first-mentioned layer.
16. A method as claimed in claim 15, wherein said first-mentioned
fabric strip of yarn material forming said first-mentioned layer
and said second fabric strip of yarn material forming said second
layer are wound mutually crosswise, such that said longitudinal
threads of the second fabric strip of yarn material in the second
layer make an angle both with said machine direction of the press
felt and with said longitudinal threads of said first-mentioned
fabric strip of yarn material in the first-mentioned layer.
17. A method as claimed in claim 11, wherein said fabric strip of
yarn material is flat-woven.
18. A method as claimed in claim 15, wherein said second fabric
strip of yarn material is flat-woven.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a press felt for use in a
papermaking machine, and to a method of manufacturing the press
felt, which is of the type comprising a woven base fabric which is
made of yarn material and is endless in the machine direction (i.e.
in the running direction of the press felt in the papermaking
machine), and one or more layers of fiber material arranged on the
base fabric.
The term "endless base fabric" as used herein and in the following
relates to a base fabric which is closed during operation. The term
"endless" should, in particular, be considered also to include the
case where the base fabric can be opened across the machine
direction for mounting in a papermaking machine, and subsequently
joined together by means of a locking seam.
The "fabric of yarn material" as mentioned above may in particular
be some type of woven or knitted fabric, and the term "fiber
material" includes all types of batt layers and %he like that can
be used in a press felt.
Currently, base fabrics for press felts are manufactured mainly by
tubular weaving technique which is known to those skilled in the
art and according to which the fabric is made in the form of a tube
or a hose-pipe and the weft threads are alternately passing into an
upper warp thread layer (upper cloth) and a lower warp thread layer
(lower cloth). The extent of this "tube" in the transverse
direction of the weaving loom thus corresponds to half the length
of the final base fabric. The width of the base fabric is
determined by the weaving length.
This known technique suffers from the following shortcomings:
1. The length of a tubular-woven base fabric is determined by the
reed width in the weaving loom. A tubular-woven base fabric thus
has a given length which
cannot be modified afterwards and which therefore, during the very
weaving operation, must be adjusted to precisely the papermaking
machine in which the press felt is to be mounted. Hence, the base
fabric and thus the press felt cannot be manufactured and kept in
stock in large series, but must be manufactured to a specific
order. This extends the delivery time and means low degree of
utilisation of the weaving equipment.
2. When adapting a weaving-loom to a longer base fabric, new warp
threads must be entered, which not only takes time, but also
involves problems in terms of quality, since after such an
adaptation of the weaving loom, it is necessary to weave one length
of useless base fabric (junk cloth) before the new warp threads
will have the correct tension in the fabric.
3. The weaving looms must be given a considerable width, preferably
over 20 m to permit tubular weaving of all current lengths of base
fabric. The weaving looms therefore become both bulky and
expensive.
4. Weaving short base fabrics in a wide weaving loom means low
degree of loom utilisation, as well as waste of thread because of
the warp threads that are not used, but yet must be fed during the
weaving procedure.
5. It is difficult to achieve uniform tension level in the
relatively large number of warp threads.
6. At the loom edges where the weaving is directed in either cloth,
it is difficult to reach the average yarn density, resulting in
irregularities at the loom edges. With such irregularities there is
a risk of inducing vibrations during operation and also markings in
the paper web.
Hence, there is a current need to solve the problems related
above.
SUMMARY OF THE INVENTION
A press felt according to the invention thus comprises an endless
base fabric of yarn material, and one or more layers of fiber
material arranged on the base fabric. The novel features of the
invention reside in that the base fabric comprises at least one
layer composed of a spirally-wound fabric strip made of yarn
material and having a width which is less than the width of the
final base fabric. The fabric strip of yarn material, preferably
being a flat-woven strip, has longitudinal threads which in the
final base fabric make an angle with the machine direction of the
press felt.
During the manufacture of the base fabric, the fabric strip of yarn
material is wound or placed spirally, preferably over at least two
rolls having parallel axes, to form said layer of the base fabric.
Thus, the length of base fabric will be determined by the length of
each spiral turn of the fabric strip of yarn material and its width
determined by the number of spiral turns.
The number of spiral turns over the total width of the base fabric
may vary. The term "strip" as used herein and in the following
relates to a piece of material having an essentially larger length
than width, the only upper limit of the strip width is that it
should be narrower than the width of the final base fabric. The
strip width may for example be 0.5-1.5 m, which should be compared
with a press felt which may be wider than 10 m.
To avoid markings in the paper web, adjoining portions of the
longitudinal edges of the spirally-wound strip are preferably so
arranged that the joints or transitions between the spiral turns
become completely smooth, i.e. such that the spirally-wound layer
has a substantially constant thickness across the entire width of
the base fabric.
The spiral turns of the strip need not necessarily be fixed to each
other, but preferably there is an edge joint between the adjoining
longitudinal edge portions of the spirally-wound strip. The edge
joint can be achieved, e.g. by sewing (for instance with
water-soluble thread), melting, and welding (for instance
ultrasonic welding), of non-woven material, or of non-woven
material with melting fibers. The edge joint can also be obtained
by providing the fabric strip of yarn material along its two
longitudinal edges with seam loops of known type, which can be
joined by means of one or more seam threads. Such seam loops may
for instance be formed directly of the weft threads, if the strip
is flat-woven.
To achieve the smooth transition between the spiral turns, these
may be arranged edge to edge or overlappingly. In the latter case,
the strip edges must however be so shaped that when being placed so
as to overlap each other, they fit into each other without giving
rise to any thickness increase at the joint. One way of achieving
this is to reduce the thickness of the edges by half as compared
with the thickness of the rest of the strip. Another way is to
increase the warp thread spacing at the edges and "interlace" the
overlapping edges, as will be described in more detail
hereinbelow.
According to an embodiment of the invention of particular interest,
two or more spirally-wound layers of the above-mentioned type are
provided, and of special interest is an embodiment in which the
spiral turns in the different layers are placed crosswise, i.e.
such that the longitudinal threads of the strip in one layer make
an angle both with the machine direction of the press felt and with
the longitudinal threads of the strip in another layer.
Other preferred embodiments and features of the invention are
recited in the dependent claims. The invention provides the
following advantages:
The weaving loom width can be considerably limited, e.g. to 0.5-1.5
m, giving low investment costs.
The fabric strip of yarn material, especially a flat-woven one, can
be manufactured and kept in stock in considerable lengths (e.g.
thousands of meters) before being dispensed from a supply reel and
placed spirally into the desired length and width of the base
fabric, which spiral arrangement can be achieved in a very short
time, e.g. in one day or less. Thus, the delivery time is
considerably cut.
It is easier to maintain a uniform quality over a small strip
width, e.g. 0.5-1.5 m, than over the relatively larger width (e.g.
6-20 m) normally used in tubular weaving, this also giving a higher
quality to the base fabric layer built up of the strip of yarn
material.
The use of flat-weaving technique gives higher production
capacity.
Variations in the thread tension across the base fabric can be
reduced considerably, since the longitudinal threads of the final
layer (=warp threads of a flat-woven strip) are not parallel to the
machine direction of the press felt. Instead, the tension at each
point becomes a mean of the tension in many different longitudinal
threads.
No irregularities are formed at the loom edges during weaving.
If two layers spirally arranged crosswise are used, particularly
interesting advantages are gained, since the longitudinal threads
in the upper base layer and in the lower base layer run in mutually
different directions. Generally, in a press nip through which the
press felt passes for dewatering a paper web, the flow of water in
the base fabric occurs substantially parallel to the longitudinal
threads. The above-mentioned crossed longitudinal threads means an
increased flow resistance, which gives an advantage in and after
the press nip. When the press felt passes the press nip, it is
compressed, thereafter to expand when leaving the press nip. During
the phase of expansion, the water which during the phase of
compression has penetrated down into the lower base layer will not
as easily return up through the upper base layer to rewet the paper
web. In this respect, it may also be noted that two or more such
spirally-applied layers can also be made with different thread
spacings in the different layers, as is known per se in
traditional, tubular-woven base fabrics of the multilayer type, to
counteract rewetting.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail hereinbelow in
some embodiments with reference to the accompanying drawings, in
which
FIG. 1 is a schematic top plan view illustrating a method of
manufacturing a base fabric for a press felt according to the
invention.
FIG. 2 is a side view corresponding to FIG. 1.
FIG. 3 shows on an enlarged scale a broken-away part of a base
fabric made according to FIGS. 1 and 2 and schematically
illustrates an angular relation between longitudinal threads in the
base fabric.
FIG. 4 is a highly simplified top plan view illustrating a method
of manufacturing a multilayer base fabric according to the
invention.
FIG. 5 is an enlarged schematic view of an edge joint between
spiral turns of a press felt according to the invention.
FIG. 6 shows a variant of the embodiment in FIG. 5, and
FIG. 7 shows another variant of the embodiment in FIG. 5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1 and 2, to which reference is now made, illustrate two
rotatably mounted rolls 10, 12 having parallel axes spaced from
each other by a distance D. At the side of one roll 12, there is
provided a supply reel 14 rotatably mounted about an axis 16 and
displaceable parallel to the rolls 10 and 12, as indicated by the
double arrow 18.
The supply reel 14 accommodates a reeled supply of a flat-woven
fabric strip of yarn material 20 having a width w. The flat-woven
strip 20 has in known manner two mutually orthoganol thread systems
consisting of longitudinal threads (warp threads) and cross threads
(weft threads) schematically represented in FIG. 1 at 22 and 24,
respectively. Further, the strip 20 has two longitudinal edges 26
and 28, the edges of which are e.g. cut before the strip 20 is
wound on to the supply reel 14.
The supply reel 14 is initially applied at the left-hand end of the
roll 12 before being continuously displaced to the right at a
synchronized speed. As the supply reel 14 is displaced sideways,
the strip 20 is dispensed, as indicated by an arrow 30, to be wound
spirally about the rolls 10, 12 into a "tube" having a closed
circumferential surface. The strip 20 is placed around the rolls
10, 12 with a certain pitch angle, which in the illustrated
embodiment is assumed to be so adapted to the strip width w, the
distance D between the roll axes and the diameters of the rolls 10,
12, that the longitudinal edges 26, 28 of adjacent "spiral turns"
32 are placed edge to edge (see FIG. 5), so as to provide a smooth
transition between the spiral turns 32.
The number of spiral turns 32 placed on the rolls 10, 12 is
dependent on the desired width B on the final base fabric. After
the spiral winding operation is completed, the edges of the
resulting base fabric are cut along the dash-dot lines 34, 36 in
FIG. 1 to obtain the width B. The length of the final base fabric
essentially is twice the distance D between the roll axes and can
therefore easily be varied by changing the distance D.
To prevent the spiral turns 32 already wound on the rolls 10, 12
from shifting on the rolls, it is possible, if so required, for
instance to fix the first turn 32 in the longitudinal direction of
the rolls.
FIG. 3, to which reference is now made, shows on an enlarged scale
a broken-away part of a base fabric produced as shown in FIGS. 1
and 2. Each longitudinal thread (warp thread) 22 of the strip 20
makes an angle a with the machine direction MD of the fabric/press
felt. These oblique longitudinal threads 22 run uninterrupted
through the entire base fabric layer, whilst the cross threads
(weft threads) 24 are interrupted and each have a length w. This is
contrary to a traditional tubular-woven endless base fabric, in
which the longitudinal threads (which in a tubular-woven fabric
consist of the weft threads) are parallel to the machine direction
and the cross threads (warp threads) run uninterrupted across the
entire width of the base fabric.
FIG. 4 illustrates most schematically, with an exaggerated small
distance between the rolls 10, 12 and with an exaggerated large
strip width w, an inventive embodiment of particular interest. Two
spirally-wound layers 40 and 42 are placed crosswise on each other,
optionally setting out from one and the same strip 20. As mentioned
above, this embodiment especially yields the advantage of an
increased flow resistance occurring, since the longitudinal threads
in both layers 40, 42 make an angle with each other. For an
embodiment according to FIG. 4, it may be possible in some cases to
dispense with the above-mentioned edge joint.
As a variant of the embodiment in FIG. 4, it is also possible to
combine a spirally-wound layer of base fabric according to the
invention with a traditionally tubular-woven layer of base fabric
to form a base fabric of multi-layer type.
For a base fabric of multilayer type, it is further possible in
known manner to use different Thread spacings/structures for the
different layers in order to obtain, for example, special
dewatering-inhibiting properties.
FIG. 5 schematically shows how the end edges 26, 28 of two
juxtaposed spiral turns 32 are in edge-to-edge relationship and
joined by sewing, as schematically indicated at 44. FIG. 5 also
schematically illustrates a top layer 46 of fiber material, such as
a batt layer, arranged on the base fabric, e.g. by needling.
As to the top layer 46 and the needling thereof, it may be
mentioned in particular that the top layer can be used for holding
together the different layers in a base fabric of multilayer type
according to FIG. 4.
FIG. 6 shows an alternative embodiment according to which adjacent
longitudinal edge portions of adjoining spiral turns are arranged
overlappingly, the edges having a reduced thickness so as not to
give rise to an increased thickness in the area of transition.
FIG. 7 shows another variant with overlapping of adjoining edge
portions. According to this alternative, the spacing between
longitudinal threads is increased at the edges 26, 28 of the strip
20, as indicated at 48, and the longitudinal threads 22 of the edge
portions are interlaced. The result is an unchanged spacing between
longitudinal threads in the area of transition, as indicated at
50.
* * * * *